m_stacks, because it's a nicely distinct and stand-alone piece of
functionality. This happily removes m_aspacemgr's dependence on
m_mallocfree (there was an apparent dependence due to the #include, even if
it didn't manifest itself in practice -- very important!) and m_options (not
so important).
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@4009
